1. Field of the Invention
The present invention relates to a backlight assembly of a flat type liquid crystal display (LCD) device, and more particularly, to a backlight assembly of an LCD device for preventing light emitted from a lamp from leaking into a liquid crystal panel without passing through a diffusion or prism sheet of the backlight assembly.
2. Discussion of the Related Art
In general, a liquid crystal display (LCD) device, one type of flat display, provides excellent visual perception as compared to a cathode-ray tube (CRT), consumes much less power than a CRT of the same size, and produces significantly less heat. Because of these features, in addition to a plasma display panel (PDP) and a field emission display (FED), the LCD has been drawing particular attention as a next generation display for cellular phones, computer monitors and TV receivers.
A typical LCD device is provided with two thin glass substrates having surfaces that have been specially treated and a liquid crystal injected between the glass substrates. The liquid crystal is in a state between solid and liquid. The arrangement of the molecules of the liquid crystal are changed according to a voltage difference between electrodes formed on the glass substrates. Changing the orientation of the liquid crystal molecules varies the light transmittance through the LCD panel so that varying degrees of brightness and darkness are generated on a display panel, thereby displaying an image. However, an LCD panel does not emit light by itself. Thus, a light source, such as a lamp, is additionally required to produce an image on the panel.
In general, in a portable or notebook computer the LCD device module includes a backlight assembly as a light source behind or along the LCD panel.
As shown in FIG. 1 to FIG. 3, the LCD module is provided with a liquid crystal panel 10, a backlight assembly 20 and a metal chassis 30.
The backlight assembly 20 for emitting light to the liquid crystal panel 10 is provided with lower and upper diffusion sheets 26 and 29, lower and upper prism sheets 27 and 28 at the rear of the liquid crystal panel 10, a light-guiding plate 24, a reflecting sheet 25, a lamp 22, a metal reflecting plate 23 surrounding the lamp 22, and a substantially rectangular mold frame 21 of synthetic resins for supporting each element. The rectangular metal chassis 30 fixes and supports each corner of the liquid crystal panel 10 and the backlight assembly 20.
In the backlight assembly of the related art LCD module, the lower diffusion sheet 26 is positioned at the lowest layer among the diffusion sheets formed on the light-guiding plate 24. The lower diffusion sheet 26 may be slightly spaced from the edge or margin of the metal reflecting plate 23 due to heat or interval between process steps, so that a gap ‘t’ is generated between the lower diffusion sheet 26 and the metal reflecting plate 23 and/or the mold frame 21. Accordingly, if light leak through the gap ‘t’, a white line is generated in the margin of the bottom of the liquid crystal panel 10.
When external force impacts on the LCD device, the sheets are moved to one side, so that the light leakage increases to further deteriorate the image display.
Accordingly, as shown in FIG. 1, a black matrix 29a is printed along the margin of the upper diffusion sheet 29 to prevent the light from leaking in the gap ‘t’ between the diffusion sheet and the metal reflecting plate 23 or mold frame 21. In another way, as shown in FIG. 2, a pad 40 may be interposed between the upper diffusion sheet 29 and the upper prism sheet 28 to prevent light from leaking in the gap ‘t’.
However, the aforementioned display devices have the following problems.
First, if the black matrix 29a is formed on the upper diffusion sheet 29 to prevent light from leaking in the gap ‘t’, manufacturing process steps are complicated.
Also, if the pad 40 is interposed between the upper diffusion sheet and the upper prism sheet to prevent light from leaking in the gap ‘t’, the thickness of the LCD device is increased, which makes the device less desirable for use in a notebook computer or other portable device.